Soil "almost frozen"? Really? You are a thousand miles south of us, and we spaded up and raked smooth the soil in a vegetable garden yesterday. I suggest glyphosate, wait a couple weeks and till-in whatever remains. Quackgrass will be the most troublesome. Keep in mind glyphosate will not persist and it will not kill weed seeds. Keep in mind that on such sites, weed seeds will sprout vigorously next year...particularly when the soil temps hit about 80. Good chance that quackgrass roots and similar rhizomes will also be a problem.

A pre-emergent like "Preen" applied in spring might help slightly...of course, it will prevent most seeds from germinating--so--your gardener would have to use plants, not seeds, in treated areas.

Ric makes a good point, plastic film will stop weeds, but a huge crop of weeds may grow up under the clear type--as the weeds benefit from the warmer temps in spring.

Yes weeds will grow under clear plastic film after you roundup that area.

In fact the Green house effect of the Clear plastic film will germinate most all seeds under that Plastic film.

So a quick Roundup treatment after the film is removed will get 99% of your early weed problems.

.

__________________
.

it is one thing to do a off label applications. It is total stupidity to post it on the world wide web and expect people to approve.